Ink jet recording medium

ABSTRACT

An ink jet recording medium which is excellent in ink absorptivity, color density, gloss, water resistance, light fastness and yellowing resistance, in particular, ink absorptivity, color density, light fastness and yellowing resistance. The ink jet recording medium comprises at least one ink receptive layer containing polymeric organic particles provided on a support, wherein the polymeric organic particles have a glass transition temperature (Tg) of 40° C. or higher and are amphoteric polymeric organic particles having both of the functional groups of a cationic group and an anionic group on the surface thereof.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an ink jet recording medium applied toa printer or plotter wherein an ink jet recording system is utilized.

2. Description of the Related Art

In recent years, the ink jet recording system can provide image qualitycomparable to that of photographs by virtue of the progress of aprinting technology. For improving the image quality, the amount of inkin printing increases and the printing is also realized at high speed,and therefore the performance which ensures that ink is absorbedinstantly and a large amount of ink is absorbed, is highly desired. Atpresent, the recording medium is mainly a void-type recording mediumthat inorganic particles such as fine particle silica and alumina areused to form a layer having voids thereon and allows ink to be absorbedthrough the void. For improving the image quality, finer inorganicparticles have been used. However, the finer the inorganic particles,the more sharply will the surface area thereof increase, and the surfaceactivity thereof increases, and thus there is a problem that lightresistance and yellowing resistance are remarkably deteriorated. Thus,it has been suggested that the organic particles are substituted for theinorganic particles.

Japanese Unexamined Patent Application Publication Nos. 2001-58461 and8-216504 disclose that in the case where the cationic additives obtainedby copolymerizing specific acrylic ester-based monomers are used withoutcombining the inorganic particles therewith, provided is a recordingmedium which is excellent in water resistance and light fastness.

However, in these cationic additives, the organic particles form closestpacking, thereby not providing sufficient voids, and thus there was aproblem that satisfactory ink absorptivity is not obtained.

In order to prevent the closest packing, there has been proposed amethod for coagulating the organic particles by a heat-sensitive gellingagent described in Japanese Unexamined Patent Application PublicationNos. 9-296067 and 9-296068. However, this method had a problem that itis difficult to control the aggregation thereof, a layer a layer havinguniform voids is not formed, and thus ink absorptivity is partly varied,the particle size of the aggregate increases, and the color density isreduced.

On the other hand, Japanese Unexamined Patent Application PublicationNo. 6-227114 discloses the applications of the amphoteric polymericorganic particles having an anionic group and a cationic group as an inkjet recording sheet. Only use of ACCOSTAR C122 (manufactured by MITSUICYANAMID, LTD.) of which the minimum film-forming temperature is 9° C.in Examples is exemplified, and the amphoteric ion latex is used as anadhesive of a pigment. In this technique, adhesiveness to the support,and surface strength and water resistance of the record sheet areimproved, and further ink absorptivity is enhanced as compared to anaqueous emulsion-type polymer latex used as a conventional adhesive.However, the amphoteric ion latex is an emulsion having a highfilm-forming ability, which is used as an adhesive, and thus if apigment is not combined therewith, ink absorption is not attained atall, thus the combination of the pigment being required. In addition, asa preferred example of the pigment, the fine particle silica isdisclosed, which is used to, make up for the deteriorated, inkabsorptivity, but light fastness and yellowing resistance cannot beprevented.

In addition, Japanese Examined Patent Application Publication No.7-45526 discloses a method for preparing a cationic latex bycopolymerizing cationic monomers, ethylenically unsaturated carboxylicacid monomers, aliphatic conjugated diene-based monomers and the othermonomers, using a cationic emulsifying agent. In the technologydescribed in the above publication, in the case where a latexessentially comprises aliphatic conjugated diene-based monomers and thelatex is applied to an ink jet recording medium, light fastness of thelatex is deteriorated due to the remaining double bonds derived from thealiphatic conjugated diene-based monomers, and thus there occurs aproblem in a long term storage of the printed matter.

It is an object of the present invention to provide, for solving theabove problems, an ink jet recording medium that is excellent in inkabsorptivity, and also in color density, water resistance, lightfastness and yellowing resistance.

SUMMARY OF THE INVENTION

The inventors have conducted intensive studies with a view to solvingthe above problems, and as a result, it has been found that an ink jetrecording medium comprising at least one ink receptive layer containingpolymeric organic particles provided on a support exhibits excellent inkabsorptivity, color density, water resistance, light fastness andyellowing resistance, by using amphoteric polymeric organic particleshaving a glass transition temperature (Tg) of 40° C. or higher andhaving a cationic group and an anionic group. The present invention hasbeen completed on the basis of this finding.

Specifically, the present invention is characterized by the following[1] to [4]:

[1] An ink jet recording medium comprising at least one ink receptivelayer containing polymeric organic particles provided on a support,wherein the polymeric organic particles have a glass transitiontemperature (Tg) of 40° C. or higher and are amphoteric polymericorganic particles having a cationic group and an anionic group;

[2] The ink jet recording medium as described in [1], wherein thepolymeric organic particles are (co)polymers of the monomers having anunsaturated double bond, or the polymeric organic particles mainlycomposed of the (co)polymers;

[3] The ink jet recording medium as described in [1] or [2], wherein thepolymeric organic particles are the polymeric organic particles obtainedby (co)polymerization of the monomers not containing aliphaticconjugated diene-based monomers; and

[4] The ink jet recording medium as described in any one of [1] to [3],wherein the weight average particle diameter of the polymeric organicparticles is from 1 to 1000 nm.

An ink jet recording medium according to the present invention is theink jet recording medium comprising at least one ink receptive layercontaining polymeric organic particles provided on a support, whereinthe polymeric organic particles have a glass transition temperature (Tg)of 40° C. or higher and are amphoteric polymeric organic particleshaving a cationic group and an anionic group. A reason why the ink jetrecording medium is excellent in ink absorptivity, color density andwater resistance is not clear, but it is presumed as follows.

Since when applying the polymeric organic particles on a support, wateris penetrated into the support and is dried to scatter, and thus thepolymeric organic particles are present at a higher concentration,leading to aggregation of the particles, and consequently water does notexist. In this process, in the case of the use of the cationic particlesand the anionic particles, it is difficult to have aggregation of theparticles, and thus it reaches approximately closest packing and thereexists no water.

On the contrary, since the amphoteric polymeric organic particles haveamphoteric ions, aggregation thereof easily occurs, and aggregationbetween the particles easily occurs before reaching the closest packing,thereby increasing voids. In addition, it is conceived that since theamphoteric polymeric organic particles of the present invention has aglass transition temperature of 40° C. or higher, dissolution and fusionof the particles in the drying process are hard to occur, the formedvoids are maintained as it is, thus ink absorptivity being excellent.Further, it is conceived that since the amphoteric polymeric organicparticles have a cationic group, an anionic dye in ink electrostaticallyis fixed, thereby color density and water resistance being excellent.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinbelow, the ink jet recording medium according to the presentinvention will be described in detail.

The ink jet recording medium according to the present invention is onecomprising at least one ink receptive layer containing amphotericpolymeric organic particles provided on a support.

The ink receptive layer as mentioned herein means all the layer whichcan absorb ink, which is provided on a support, and in the case of anink jet recording medium comprising a plurality of ink receptive layersprovided on a support, the polymeric organic particles of the presentinvention are contained in at least one of the ink jet receptive layers.

The amphoteric polymeric organic particles having an anionic group and acationic group of the present invention have a glass transitiontemperature (Tg) of 40° C. or higher, preferably 60° C. or higher. Whenthe glass transition temperature (Tg) is less than 40° C., fusionbetween the particles leads to easy reduction of voids to therebydeteriorate the ink absorptivity.

In addition, the glass transition temperature (Tg) referred to in thepresent invention can be determined from DSC curve in accordance with onJIS K 7121.

In the present invention, as a method wherein an anionic group isintroduced into the amphoteric polymeric organic particles having ananionic group and a cationic group, there can be mentioned a methodwherein an initiator having an anionic group is used, a method whereinthe monomers having an anionic group are used, and a method wherein asurfactant having an anionic group is used. In addition, as a methodwherein a cationic group is introduced, there can be mentioned a methodwherein an initiator having a cationic group is used, a method whereinthe monomers having a cationic group are used, and a method wherein asurfactant having a cationic group is used. In the case where as themethod wherein an anionic group is introduced, the monomers having theanionic group are used, and as the method wherein the cationic group isintroduced, the initiator having the cationic group and the surfactanthaving the cationic group are used, the stability of the polymericorganic particles to be polymerized is improved, thus it being apreferred embodiment.

In addition, as a preferred embodiment of the amphoteric polymericorganic particles of the present invention, there may be mentioned a(co)polymer of the monomers having an unsaturated double bond, or thepolymeric organic particles comprising the (co)polymer as a maincomponent. The polymeric organic particles mainly composed of the(co)polymer as mentioned herein mean composite polymeric organicparticles of a (co)polymer of the monomers having an unsaturated doublebond and other components, for example, inorganic particles such assilica and polymers such as aqueous urethanes and olefins, or a compoundreferred to as an ultraviolet absorber and a fluorescent brightener, the(co)polymer of the monomers having an unsaturated double bond beingcontained in an amount of usually 50% by weight or more in terms of thesolid content thereof.

Examples of the monomer having an unsaturated double bond include:

aromatic vinyl monomers such as styrene, 2-methylstyrene,t-butylstyrene, chlorostyrene, vinylanisole, and vinylnaphthalene;

acrylic esters such as isopropyl acrylate, n-butyl acrylate, isobutylacrylate, t-butyl acrylate, n-hexyl acrylate, 2-ethylhexyl acrylate,octyl acrylate, decyl acrylate, dodecyl acrylate, octadecyl acrylate,methyl acrylate, ethyl acrylate, cyclohexyl acrylate, phenyl acrylate,benzyl acrylate, isoboronyl acrylate, and other alkyl acrylates having 3to 20 carbon atoms;

methacrylic esters such as isopropyl methacrylate, n-butyl methacrylate,isobutyl methacrylate, t-butyl metharylate, n-hexyl methacrylate,2-ethylhexyl methacrylate, octyl methacrylate, decyl methacrylate,dodecyl methacrylate, octadecyl methacrylate, methyl methacrylate, ethylmethacrylate, cyclohexyl methacrylate, phenyl methacrylate, benzylmethacrylate, isoboronyl methacrylate, and other methacrylates having 3to 20 carbon atoms;

hydroxyl group-containing vinyl monomers such as 2-hydroxyethylacrylate, hydroxypropyl acrylate, 4-hydroxybutyl acrylate,2-hydroxyethyl methacrylate, hydroxypropyl methacrylate, and4-hydroxybutyl methacrylate;

amides such as acrylamide, methacrylamide, N-methylolmethacrylamide,N-methylolacrylamide, diacetone acrylamide, and maleic acid amide;

halogenated vinylidene monomers such as vinylidene chloride andvinylidene fluoride;

vinyl esters such as vinyl acetate and vinyl propionate; and

other monomers such as chloroethylene, vinyl ether, vinyl ketone,vinylamide, chloroprene, ethylene, propylene, vinylpyrrolidone,2-methoxyethyl acrylate, 2-ethoxyethyl acrylate, glycidyl acrylate,glycidyl methacrylate, allyl glycidyl ether, acrylonitrile,methacrylonitrile, 1,2,2,6,6-pentamethyl-4-piperidyl (meth)acrylate,2,2,6,6-tetramethyl-4-piperidyl (meth)acrylate, and2-(2′-hydroxy-5′-methacryloyloxyethylphenyl)-2H-benzotriazole.

In addition, examples of the monomer having an anionic group include:

unsaturated carboxylic acid monomers such as acrylic acid, methacrylicacid, itaconic acid, maleic acid, fumaric acid, acrylic anhydride,methacrylic anhydride, maleic anhydride, itaconic anhydride, and fumaricanhydride;

unsaturated sulfonic acid monomers such as styrenesulfonic acid, sodiumstyrenesulfonate, and 2-acrylamide-2-methylpropanesulfonic acid; and

unsaturated phosphoric acid monomers such asmono(2-methacryloyloxyethyl) phosphate and mono(2-acryloyloxyethyl)phosphate.

In addition, examples of the monomer having a cationic group include:

monomers having a tertiary amino group, e.g., N,N-dialkylaminoalkylacrylates and N,N-dialkylaminoalkyl methacrylates, such asN,N-dimethylaminoethyl acrylate, N,N-dimethylaminoethyl methacrylate,N,N-dimethylaminopropyl acrylate, N,N-dimethylaminopropyl methacrylate,N,N-diethylaminoethyl acrylate, N,N-diethylaminoethyl methacrylate,N,N-diethylaminopropyl acrylate and N,N-diethylaminopropyl methacrylate;N,N-dialkylacrylamides and N,N-dialkylmethacrylamides, such asN,N-dimethylacrylamide, N,N-dimethylmethacrylamide,N,N-diethylacrylamide and N,N-diethylmethacrylamide;N,N-dialkylaminoalkylacrylamides andN,N-dialkylaminbalkylmethacrylamides, such asN,N-dimethylaminopropylacrylamide, N,N-dimethylaminopropylmethacrylamide, N,N-dimethylaminoethylacrylamide andN,N-dimethylaminoethylmethacrylamide; and other N-isopropylacrylamideand N,N-dimethylamino(2-hydroxy)propyl ethacrylate; and

monomers having a quaternary ammonium group, wherein the monomers havinga tertiary amino group are quaternized with a halogenated methyl group,a halogenated ethyl group, and a halogenated benzyl group, which arehalogenated with a halogen atom such as chlorine, bromine and iodine.

In addition, for the purpose of improving the heat resistance of thepolymeric organic particles or other purposes, there can also be usedtogether with a crosslinking agent such as ethylene glycoldimethacrylate, diethylene glycol dimethacrylate, triethylene glycoldimethacrylate, polyethylene glycol dimethacrylate, polypropylene glycoldimethacrylate, neopentyl glycol dimethacrylate, 1,3-butylene glycoldimethacrylate, 1,6-hexanediol dimethacrylate, neopentyl glycoldimethacrylate, polyethylene glycol diacrylate, 1,6-hexanedioldiacrylate, neopentyl glycol diacrylate, tripropylene glycol diacrylate,polypropylene glycol diacrylate, trimethylolpropane trimethacrylate,trimethylolpropane triacrylate, tetramethylolmethane triacrylate,tetramethylolmethane tetraacrylate, allyl methacrylate, dicyclopentenylacrylate, dicyclopentenyloxyethyl acrylate,isopropenyl-α,α-dimethylbenzyl isocyanate, allyl mercaptan,divinylbenzene and methylene bisacrylamide.

In addition, when a (co)polymer is obtained, if necessary, as amolecular weight modifier, mercaptans such as t-dodecyl mercaptan andn-dodecyl mercaptan, an allyl compound such as allylsulfonic acid,methallylsulfonic acid and the sodium salts thereof, or the like can beused.

An average particle diameter of the amphoteric polymeric organicparticles having an anionic group and a cationic group, according to thepresent invention, is preferably 1 nm to 1000 nm, more preferably 1 nmto 500 nm, even more preferably 1 to 300 nm. When the average particlediameter is less than 1 nm, insufficient voids may be provided and thusthe ink absorptivity may be lowered, while when it exceeds 1000 nm, thecolor density may be lowered.

The weight average molecular weight of the amphoteric polymeric organicparticles having an anionic group and a cationic group of the presentinvention is 10000 or more, more preferably 30000 or more, even morepreferably 60000 or more. With the weight average molecular weight ofless than 10000, the deformation of organic particles may be likely tooccur to thereby reduce voids, and thus the ink absorptivity may bedeteriorated.

The amphoteric polymeric organic particles having an anionic group and acationic group in the present invention can be produced according to aconventionally well-known emulsion polymerization process or amechanical emulsification process. For example, in the emulsionpolymerization process, there can be employed a method wherein variousmonomers are simultaneously charged and polymerized in the presence of adispersant and an initiator and a method wherein monomers arecontinuously fed and polymerized. In the emulsion polymerizationprocess, the polymerization temperature is usually 30 to 90° C., andthus substantially a water dispersion of the organic particles can beobtained.

The initiator for use in the production of the polymeric organicparticles of the present invention, can be any initiators for use in acommon emulsion polymerization, and examples thereof include:

as an initiator having a cationic group, 2,2′-azobis(2-amidinopropane)dihydrochloride, 2,2′-azobis[2-(N-phenylamidino)propane]dihydrochloride,2,2′-azobis{2-[N-(4-chlorophenyl)amidino]propane}dihydrochloride,2,2′-azobis{2-[N-(4-hydroxyphenyl)amidino]propane}dihydrochloride,2,2′-azobis[2-(N-benzylamidino)propane]dihydrochloride,2,2′-azobis[2-(N-allylamidino)propane]dihydrochloride,2,2′-azobis{2-[N-(2-hydroxyethyl)amidino]propane}dihydrochloride,2,2′-azobis(2-methylbutaneamidoxime) dihydrochloride, or the like;

as an anionic initiator, persulfates such as ammonium persulfate,potassium persulfate and sodium persulfate, or the like;

as a nonionic initiator, organic peroxides such as cumene hydroperoxide,t-butyl hydroperoxide, benzoyl peroxide, t-butylperoxy-2-ethylhexanoate,t-butylperoxybenzoate and lauroyl peroxide and azo compounds such asazobisisobutyronitrile,2,2′-azobis{2-methyl-N-[1,1-bis(hydroxymethyl)-2-hydroxyethyl]propionamide},2,2′-azobis{2-methyl-N-[1,1-bis(hydroxymethyl)ethyl]propionamide},2,2′-azobis[2-methyl-N-[2-hydroxyethyl]propionamide] and2,2′-azobis(isobutylamide) dihydrate.

The dispersant for use in the production of the polymeric organicparticles of the present invention, can be the dispersant used in acommon emulsion polymerization, and particularly a cationic surfactant,an amphoteric surfactant, a nonionic surfactant or the like arepreferably used.

The cationic surfactant includes, for example, alkyltrimethylammoniumchlorides such as lauryltrimetylammonium chloride,stearyltrimethylammonium chloride and cetyltrimethylammonium chloride;dialkyldimethylammonium chlorides such as distearyldimethylammoniumchloride; alkylamine salts such as coconut amine acetate andstearylamine acetate; alkylbenzyl dimethylammonium chlorides such aslaurylbenzyldimethylammonium chlorides; alkylamine guanidinepolyoxylethanol; and alkylpicolinium chloride. One, or two or more kindscan be selected from these.

The amphoteric surfactant includes, for example,alkyldimethylaminoacetic acid betaines such as lauryldimethylaminoaceticacid betaine and stearyldimethylaminoacetic acid betaine; alkyldimethylamine oxides such as lauryl dimethylamine oxide and stearyldimethylamine oxide; alkylcarboxymethylhydroxyethylimidazoliniumbetaine, alkylamidopropyl betaine, and alkylsulfobetaine. One, or two ormore kinds can be selected from these.

Specific examples of the nonionic surfactant includes, for example,polyoxyethylene lauryl ether, polyoxyethylene octylphenyl ether,polyoxyethylene oleylphenyl ether, polyoxyethylene nonylphenyl ether,oxyethylene-oxypropylene block copolymer,tert-octylphenoxyethylpolyethoxyethanol, andnonylphenoxyethylpolyethoxyethanol. One, or two or more kinds can beselected from these.

Cationic or anionic particles can also be used in combination with theamphoteric polymeric organic particles having an anionic group and acationic group of the present invention. When coating and drying onlysuch cationic or anionic particles on a support, closest packing thereofleads to the deterioration of the ink absorptivity, but the existence ofthe amphoteric particles suppresses closest packing, giving excellentink absorptivity. As the cationic or anionic particles, inorganicparticles or organic particles can be used, but the cationic organicparticles are preferred because they may provide excellent colordensity, light fastness and water resistance.

The ink jet recording medium according to the present invention maycomprise a polymer having a binder function for the purpose of improvingsurface strength and gloss. The polymer having binder function includes,for example, a water dispersion of a water soluble polymer or a waterinsoluble polymer, or the like. Hereinbelow, it will be described indetail.

The water soluble polymer includes, for example, as the cationic watersoluble polymer, cationized polyvinyl alcohol, cationized starch,cationized polyacrylamide, cationized polymethacrylamide,polyamidopolyurea, polyethyleneimine, a copolymer of allylamine or itssalt, an epichlorohydrin/dialkyl amine adduct polymer, a polymer ofdiallylalkylamine or its salt, a polymer of a diallyldialkylammoniumsalt, a copolymer of diallylamine or its salt and sulfur dioxide, adiallyldialkylammonium salt/sulfur dioxide copolymer, a copolymer ofdiallyldialkylammonium salt and diallylamine or its salt or a derivativethereof, a copolymer of a quaternary salt ofdialkylaminoethyl(meth)acrylate, a diallyldialkylammoniumsalt/acrylamide copolymer, an amine/carboxylic acid copolymer or thelike.

Further, it also includes, as a nonionic water soluble polymer,polyvinyl alcohol or its derivative; starch derivatives such as oxidizedstarch, etherified starch or phosphate esterified starch; polyvinylpyrrolidone or a polyvinyl pyrrolidone derivative such as polyvinylpyrrolidone obtained by copolymerization with vinyl acetate; cellulosederivatives such as carboxymethyl cellulose and hydroxymethyl cellulose;polyacrylamide or its derivative; polymethacrylamide or its derivative;gelatin; casein or the like.

Further, the water dispersion of the water insoluble polymer includes,for example,

a water dispersion of a cationic and/or nonionic acrylic polymer (apolymer or copolymer of acrylic ester and/or methacrylic ester), an MBRpolymer (a methyl methacrylate/butadiene copolymer), an SBR polymer (astyrene/butadiene copolymer), an urethane polymer, an epoxy polymer oran EVA polymer (an ethylene/vinyl acetate copolymer).

A water dispersion of polyvinyl alcohol, cationized polyvinyl alcohol oran acrylic polymer (a polymer or copolymer of acrylic ester and/ormethacrylic ester) is preferably used, particularly from the viewpointof the characteristics of excelling in yellowing resistance. Inaddition, use of a cationic water soluble polymer or a cationic waterinsoluble polymer is preferable because it gives improved color densityor water resistance.

In addition, the ink jet recording medium according to the presentinvention may include, in addition to these, a wetting agent, anantistatic agent, an antioxidant, a dry paper strength additive, a wetpaper strength additive, a waterproofing agent, an antiseptic agent, anultraviolet absorber, a photostabilizer, a fluorescent brightener, acoloring pigment, a coloring dye, a penetrant, a blowing agent, a moldrelease agent, a foam inhibitor, a defoaming agent, a fluidity improver,and a thickening agent or the like.

In addition, the recording medium having excellent ink absorptivity maybe obtained by comprising a layer containing a pigment such as silicawith excellent ink absorptivity which is superimposed in sequence on asupport, and an adhesive such as polyvinyl alcohol as a binder thereofand a layer containing the polymeric organic particles according to thepresent invention.

In the present invention, as the support, use can be made of supportsconventionally used in the ink jet recording sheets, for example, apaper support such as plain paper, art paper, coated paper, cast coatedpaper, resin coated paper, resin impregnated paper, noncoated paper andcoated paper; a paper support having its both sides coated withpolyolefin, a plastic support, a nonwoven fabric, a cloth, a wovenfabric, a metal film, a metal plate and a composite support consistingof a laminate of these.

As the plastic support, there can preferably be used, for example, asheet or film of plastic such as polyethylene, polypropylene,polystyrene, polyethylene terephthalate, polyethylene naphthalate,triacetylcellulose, polyvinyl chloride, polyvinylidene chloride,polyimide, polycarbonate, cellophane, and polynylon. Among these plasticsupports, transparent, translucent or opaque ones can appropriately beselected according to intended use.

It is also preferred to use a white plastic film as the support. As thewhite plastic support, use can be made of a support constituted of aplastic compounded with a small amount of a white pigment such as bariumsulfate, titanium oxide and zinc oxide, a foamed plastic supportprovided with opacity by forming a multiplicity of minute voids, or asupport furnished with a layer containing a white pigment (titaniumoxide or barium sulfate).

In the present invention, although the configuration of the support isnot limited, not only customarily employed films, sheets and plates butalso cylindrical forms such as that of a drink can, disc forms as thatof CD or CD-R and other complex forms can be used as the support.

In the present invention, when the polymeric organic particles arecoated on a support, use can be made of, for example, conventionallyknown application techniques by means of an air knife coater, a rollcoater, a bar coater, a blade coater, a slide hopper coater, a gravurecoater, a flexogravure coater, a curtain coater, an extrusion coater, afloating knife coater, a comma coater, a die coater or the like.

Further, when it is intended to impart gloss to the coating surface, forexample, a common calendering treatment can be applied. For example,there can be used the conventionally known method wherein with the useof a calendar machine such as a supercalender and a gloss calender, therecording medium is passed through gap between rolls having pressure andheat applied thereto so as to smooth the surface of the coating layer.In addition, a cast coating technique such as a direct method, asolidification method, a re-wetting method and a precasting method,which is generally used in the production of a cast coated paper forprinting, can also be preferably used.

EXAMPLES

The present invention will be further described below with reference tothe following Examples, which however in no way limit the scope of thepresent invention. Herein, the parts and % refer to parts by weight and% by weight, respectively, unless otherwise specified.

Example 1

<Production of Amphoteric Polymeric Organic Particles having an AnionicGroup and a Cationic Group>

600.0 parts of deionized water and 1.5 parts of lauryltrimethylammomiumchloride were charged into a reaction vessel, and the pH of the mixturewas adjusted to 2 with an aqueous hydrochloric acid solution. Thereaction mixture was heated to 65° C. in a nitrogen stream, and 3.0parts of 2,2′-azobis(2-amidinopropane) dihydrochloride was added to themixture. Separately, 120.0 parts of styrene, 135.0 parts of t-butylmethacrylate, 30.0 parts of 2-hydroxyethyl methacrylate and 15.0 partsof methacrylic acid were emulsified into 120.0 parts of deionized waterin the presence of 6.0 parts of lauryltrimethylammonium chloride tothereby obtain an emulsified mixture. This emulsified mixture wasdropped into the reaction vessel over a period of 4 hours. Thereafter,the mixture was maintained at the same temperature for 4 hours and thenthe nonvolatile content thereof was adjusted to 30% with deionizedwater. As a result, an aqueous composition consisting of the amphotericpolymeric organic particles having an anionic group and a cationic groupdispersed in water was obtained. The aqueous composition had thenonvolatile content of 30% and the pH of 2.7. The polymeric organicparticles had the average particle diameter of 70 nm as determined byobservation through an electron microscope and the glass transitiontemperature (Tg) of 105° C.

<Production of Recording Sheet>

A wood free paper having a basis weight of 105 g/m² was coated with theaqueous composition of the amphoteric polymeric organic particles havingan anionic group and a cationic group dispersed in water so that thecoating amount was 20 g/m² in absolute dry condition, and the resultantcoating layer was subjected to the cast coating process, specificallypressing the coating layer surface against a specular roll of 70° C.surface temperature at a linear pressure of 50 kg/cm and effectingdrying. As a result, a recording sheet of Example 1 was obtained.

Example 2

<Production of Amphoteric Polymeric Organic Particles having an AnionicGroup and a Cationic Group>

600.0 parts of deionized water and 1.5 parts of lauryltrimethylammomiumchloride were charged into a reaction vessel, and the pH of the mixturewas adjusted to 2 with an aqueous hydrochloric acid solution. Thereaction mixture was heated to 65° C. in a nitrogen stream, and 3.0parts of 2,2′-azobis(2-amidinopropane) dihydrochloride was added to themixture. Separately, 120.0 parts of styrene, 144.0 parts of t-butylmethacrylate, 30.0 parts of 2-hydroxyethyl methacrylate and 6.0 parts ofmethacrylic acid were emulsified into 120.0 parts of deionized water inthe presence of 6.0 parts of lauryltrimethylammonium chloride to therebyobtain an emulsified mixture. This emulsified mixture was dropped intothe reaction vessel over a period of 4 hours. Thereafter, the mixturewas maintained at the same temperature for 4 hours and then thenonvolatile content thereof was adjusted to 30% with deionized water. Asa result, an aqueous composition consisting of the amphoteric polymericorganic particles having an anionic group and a cationic group dispersedin water was obtained. The aqueous composition had the nonvolatilecontent of 30% and the pH of 2.7. The polymeric organic particles hadthe average particle diameter of 65 nm as determined by observationthrough an electron microscope and the glass transition temperature (Tg)of 103° C.

<Production of Recording Sheet>

Using the above obtained aqueous composition, a recording sheet wasproduced in the same manner as in Example 1.

Comparative Example 1

<Production of Cationic Organic Particles>

600.0 parts of deionized water and 1.5 parts of lauryltrimethylammomiumchloride were charged into a reaction vessel and heated to 65° C. in anitrogen stream. 3.0 parts of 2,2′-azobis(2-amidinopropane)dihydrochloride was added to the mixture. Separately, 150.0 parts ofstyrene, 135.0 parts of methyl methacrylate and 15.0 parts of2-hydroxyethyl methacrylate were emulsified into 120.0 parts ofdeionized water in the presence of 1.2 parts of lauryltrimethylammoniumchloride to thereby obtain an emulsified mixture. This emulsifiedmixture was dropped into the reaction vessel over a period of 4 hours.Thereafter, the mixture was maintained at the same temperature for 4hours and then the nonvolatile content thereof was adjusted to 30% withdeionized water. As a result, an aqueous composition consisting of thecationic polymeric organic particles dispersed in water was obtained.The aqueous composition had the nonvolatile content of 30% and the pH of5.4. The polymeric organic particles had the average particle diameterof 70 nm as determined by observation through an electron microscope andthe glass transition temperature (Tg) of 103° C.

<Production of Recording Sheet>

Using the above obtained aqueous composition, a recording sheet wasproduced in the same manner as in Example 1.

Comparative Example 2

<Production of Anionic Organic Particles>

600.0 parts of deionized water and 0.6 part of sodiumdodecylbenzenesulfonate were charged into a reaction vessel, and heatedto 70° C. in a nitrogen stream. 1.8 parts of potassium persulfate wasadded to the mixture. Separately, 75.0 parts of styrene, 180.0 parts ofmethyl methacrylate, 30.0 parts of 2-hydroxyethyl methacrylate and 15.0parts of methacrylic acid were emulsified into 120.0 parts of deionizedwater in the presence of 0.6 part of sodium dodecylbenzensulfonate tothereby obtain an emulsified mixture. This emulsified mixture wasdropped into the reaction vessel over a period of 4 hours. Thereafter,the mixture was maintained at the same temperature for 4 hours and thenthe nonvolatile content thereof was adjusted to 30% with deionizedwater. As a result, an aqueous composition consisting of the anionicpolymeric organic particles dispersed in water was obtained. The aqueouscomposition had the nonvolatile content of 30% and the pH of 2.4. Thepolymeric organic particles had the average particle diameter of 105 nmas determined by observation through an electron microscope and theglass transition temperature (Tg) of 105° C.

<Production of Recording Sheet>

Using the above obtained aqueous composition, a recording sheet wasproduced in the same manner as in Example 1.

Comparative Example 3

<Production of Amphoteric Polymeric Organic Particles with a Low Tg>

600.0 parts of deionized water and 1.5 parts of lauryltrimethylammomiumchloride were charged into a reaction vessel, and the pH of the mixturewas adjusted to 2 with an aqueous hydrochloric acid solution. Thereaction mixture was heated to 65° C. in a nitrogen stream, and 3.0parts of 2,2′-azobis(2-amidinopropane) dihydrochloride was added to themixture. Separately, 120.0 parts of styrene, 144.0 parts of n-butylacrylate, 30.0 parts of 2-hydroxyethyl methacrylate and 6.0 parts ofmethacrylic acid were emulsified into 120.0 parts of deionized water inthe presence of 6.0 parts of lauryltrimethylammonium chloride to therebyobtain an emulsified mixture. This emulsified mixture was dropped intothe reaction vessel over a period of 4 hours. Thereafter, the mixturewas maintained at the same temperature for 4 hours and then thenonvolatile content thereof was adjusted to 30% with deionized water. Asa result, an aqueous composition consisting of the amphoteric polymericorganic particles having an anionic group and a cationic group dispersedin water was obtained. The aqueous composition had the nonvolatilecontent of 30% and the pH of 2.9. The polymeric organic particles hadthe average particle diameter of 68 nm as determined by observationthrough an electron microscope and the glass transition temperature (Tg)of 16° C.

<Production of Recording Sheet>

Using the above obtained aqueous composition, a recording sheet wasproduced in the same manner as in Example 1.

Comparative Example 4

<Production of Amphoteric Polymeric Organic Particles byCopolymerization of Diene Monomers>

792.0 parts of deionized water, 0.6 part of lauryltrimethylammoniumchloride, 15 parts of 2,2′-azobis(2-amidinopropane) dihydrochloride,260.0 parts of styrene, 35.0 parts of methyl methacrylate, 15.0 parts ofmethacrylic acid and 15.0 parts of butadiene were charged into anautoclave, and heated to 50° C. in a nitrogen stream. When thepolymerization conversion reached 80% and the reaction mixture washeated to 60° C. When the polymerization conversion reached 99%, thereaction mixture was cooled to remove the unreacted materials in theemulsion by stripping and thus to obtain an aqueous compositionconsisting of the amphoteric polymeric organic particles dispersed inwater. The nonvolatile content of the aqueous composition was adjustedto 30% with deionized water. The aqueous composition had the nonvolatilecontent of 30% and the pH of 5.3. The polymeric organic particles hadthe average particle diameter of 80 nm as determined by observationthrough an electron microscope and the glass transition temperature (Tg)of 93° C.

<Production of Recording Sheet>

Using the above obtained aqueous composition, a recording sheet wasproduced in the same manner as in Example 1.

Comparative Example 5

<Use of Commercially Available Amphoteric Polymeric Organic Particles>

<Production of Recording Sheet>

Using of ACCOSTAR C122 [manufactured by Mitsui Cytec Co., Ltd.] whichwas a commercially available amphoteric latex (a solid content 40%, aparticle diameter 0.2 μm, and a minimum film-forming temperature 9° C.),a recording sheet was produced in the same manner as in Example 1.

[Method of Evaluation]

The quality evaluation results of the recording sheets are listed inTables 1 and 2. The evaluation was conducted in the following manner.

<Method of Measuring Gloss>

In the gloss measurement, the level of gloss at 60° C. of the surface ofthe recording sheet was measured by means of deformation glossmetermodel GM-3D (manufactured by Murakami Color Research Laboratory) inaccordance with JIS Z8741.

<Method of Measuring Color Density>

Solid printing with black ink and cyan ink was performed effected oneach recording sheet by means of a commercially available ink jetprinter (PM2000C manufactured by Seiko Epson Corporation). The opticalreflection density of a solid part was measured by means of Macbethdensitometer (RD-918).

<Method of Measuring Ink Absorptivity>

For evaluating ink absorptivity, setting property and image irregularitywere evaluated.

(Setting Property)

Solid printing of each of yellow ink, magenta ink, cyan ink and blackink was effected in the longitudinal direction of the recording sheet bymeans of a commercially available ink jet printer (PM800C manufacturedby Seiko Epson Corporation). Immediately after delivery from theprinter, PPC paper was pressed onto the upper surface of the recordingsheet, and the degree of transfer of ink from the recording sheet to thePPC paper was evaluated by visual inspection. The evaluation criteriawere as follows:

◯: No ink transfer was observed, thereby attesting to excellent inkabsorptivity;

Δ: Slight ink transfer was observed, but the ink absorptivity was apracticable level; and

x: Ink transfer was extensive, so that the ink absorptivity was below apractical level.

(Image Irregularity)

Female photograph of highly fine color digital standard image data(ISO/JIS-SCID) was printed on the recording sheet by means of acommercially available ink jet printer (PM800C manufactured by SeikoEpson Corporation), and image irregularity was evaluated by visualinspection. When the ink absorptivity is poor, image irregularity occursdue to insufficient ink absorption. The evaluation criteria were asfollows:

◯: No image irregularity was observed, thereby attesting to excellentink absorptivity;

Δ: Slight image irregularity was observed, but the ink absorptivity wasa practicable level; and

x: Image irregularity was extensive, and hence the ink absorptivity wasbelow a practical level.

<Method of Measuring Water Resistance>

Character printing with black ink was effected by means of acommercially available ink jet printer (PM800C manufactured by SeikoEpson Corporation). One drop of city water was placed on the printedportion, and allowed to stand still round the clock. Thereafter, theprint condition was evaluated by visual inspection. The evaluationcriteria were as follows:

◯: There was almost no bleeding;

Δ: Slight bleeding was observed, but a practical level; and

x: Bleeding was observed, and hence below a practical level.

<Method of Measuring Light Fastness>

Solid printing with magenta ink was effected on each recording sheet bymeans of a commercially available ink jet printer (PM800C manufacturedby Seiko Epson Corporation). The printed recording sheet was exposed tolight for 100 hours by means of a xenon fadeometer, and the residualratio of the optical reflection density after light exposure, relativeto the optical reflection density before light exposure was measured andreferred to as light fastness. The optical reflection density wasmeasured by means of Macbeth densitometer (RD-918).

<Method of Measuring Yellowing Resistance>

The unprinted recording sheet was exposed to light for 7 hours by meansof a carbon arc fadeometer, and the difference between color beforelight exposure and color after light exposure was measured. The colordifference (ΔE) in terms of L*a*b* (expression method according to CIE)was calculated by the formula ΔE={(ΔL*)²+(Δa*)²+(Δb*)²}^(1/2) from theresults of measuring of color before the light exposure and color afterthe light exposure. The larger the color difference, the more seriousthe color deterioration. TABLE 1 Properties of polymeric organicparticles Ink absorptivity Ionic property Tg of Setting Image Colordensity of particles particles property irregularity Black Cyan Ex. 1Amphoteric 105° C. ∘ ∘ 2.05 1.98 Ex. 2 Amphoteric 103° C. ∘ ∘ 2.07 1.97Com. Ex. 1 Cationic 103° C. Δ x 2.05 1.98 Com. Ex. 2 Anionic 105° C. Δ x1.24 1.33 Com. Ex. 3 Amphoteric  16° C. x x Unmeasurable UnmeasurableCom. Ex. 4 Amphoteric  93° C. Δ Δ 1.88 1.82 Com. Ex. 5 Amphoteric (MFT9° C.) x x Unmeasurable UnmeasurableMFT: Minimum film-forming temperature

TABLE 2 Water Light Yellowing Gloss resistance fastness resistance Ex. 163 ∘ 84% 1.1 Ex. 2 59 ∘ 85% 1.1 Com. Ex. 1 53 ∘ 85% 1.1 Com. Ex. 2 54 x64% 1.2 Com. Ex. 3 50 Unmeasurable Unmeasurable Unmeasurable Com. Ex. 452 ∘ 48% 1.8 Com. Ex. 5 47 Unmeasurable Unmeasurable Unmeasurable

According to the present invention, there can be obtained an ink jetrecording medium which is excellent in ink absorptivity, color density,gloss, water resistance, light fastness and yellowing resistance, inparticular, ink absorptivity, color density, light fastness andyellowing resistance.

1. An ink jet recording medium comprising at least one ink receptivelayer containing polymeric organic particles provided on a support,wherein the polymeric organic particles have a glass transitiontemperature (Tg) of 40° C. or higher and are amphoteric polymericorganic particles having a cationic group and an anionic group.
 2. Theink jet recording medium according to claim 1, wherein the polymericorganic particles are (co)polymers of monomers having an unsaturateddouble bond, or the polymeric organic particles are comprised of the(co)polymers.
 3. The ink jet recording medium according to claim 1,wherein the polymeric organic particles are the polymeric organicparticles obtained by (co)polymerization of the monomers not containingaliphatic conjugated diene-based monomers.
 4. The ink jet recordingmedium according to claim 3, wherein the weight average particlediameter of the polymeric organic particles is from 1 to 1000 nm.
 5. Theink jet recording medium according to claim 1, wherein the weightaverage particle diameter of the polymeric organic particles is from 1to 1000 nm.
 6. The ink jet recording medium according to claim 2,wherein the weight average particle diameter of the polymeric organicparticles is from 1 to 1000 nm.